Plural movable core transformer assembly with escapement means



p 13, 1966 o. MULLER-GIRARD 3,273,100

PLURAL MOVABLE CORE TRANSFORMER ASSEMBLY WITH ESCAPEMENT MEANS OriginalFiled April 29, 1960 Ill mvsmoa Orro Muller-Girord United States Patent3 273 100 PLURAL MOVABLE flOliE TRANSFORMER AS- SEMBLY WITH ESCAPEMENTMEAN Otto Muller-Girard, Rochester, N.Y., assignor to Taylor InstrumentCompanies, Rochester, N.Y., a corporation of New York Originalapplication Apr. 29, 1960, Ser. No. 25,637, now Patent No. 3,173,003,dated Mar. 9, 1965. Divided and this application Dec. 8, 1964, Ser. No.423,409

7 Claims. (Cl. 336-131) This application for US. Letters Patents is adivision of my prior copending application Ser. No. 25,637, filed April29, 1960, and now Patent No. 3,173,003, issued March 9, 1965.

As disclosed in said patent, a measuring system of the null-balance typeis caused to compute square root of an input signal by balancing saidsignal against, in effect, said signal multiplied by itself. Themultiplication is achieved by means of a pair of movable coretransformers arranged to electrically multiply, in effect, the inputsignal by itself, and by means of a servo arrangement moving the coresof the transformers as one, as is known in the art, to make themultiplied input signal equal to itself, with the result that theposition of the said cores becomes a measure of the square root of theinput signal. As disclosed further in said patent, the multiplication ofthe input signal causes difficulties at values of input signal in thevicinity of zero magnitude of said input signal, which are obviated bymoving one core only when said input signal is in said vicinity.

The present invention relates to escapement means for controllingmovement of said cores, and the object of the invention being to providethe combination including a plural movable core transformer assembly andescapement means so arranged that when the cores of said assembly aremoved, they move together, except that in one part of their range ofmovement the escapement means acts to allow but one of said cores tomove in that part.

In the drawings:

FIGURE 1 shows a pair of movable core transformers having their coresarranged for movement together under control of escapement means, asaforesaid;

FIGURE 2 is an enlarged view in section on the lines -5 of FIGURE 1; and

FIGURE 3 is an elevation of a detail of FIGURE 1.

The transformers of FIGURE 1 are shown to be linear variabledifferential transformers (LVDTs) 31 and 41 including primary windings32 and 42, secondary windings 33 and 43, and cores 34 and 44,respectively. The electrical arrangement is illustrated to be, broadly,that disclosed in my aforesaid patent. Thus, primary winding 42 isenergized by an electrical source 3, and couples the voltage acrossitself to the secondary winding 43 by transformer action. Secondarywinding 43 energizes primary winding 32 via suitable interconnectingmeans, say amplifier 40 of my said patent, and the voltage acrosswinding 32 is coupled to secondary winding 33 by transformer action.Secondary winding 33 is connected to any suitable means, such as thedifferential amplifier 50. The described arrangement, as is well known,provides the means 50 with a voltage that is a function of the square ofthe voltage across winding 43. The magnitude of the voltage acrosswinding 33 also depends on the positions of cores 34 and 44. Thus, ifthe position of each core is changed, and each such change is such aswould, say, increase the voltage across winding 33, such voltageincrease is a function of the product of core position changes.

In the mechanism illustrated in FIGURE 1 moving cores 34 and 44, arotary cam 62 is mounted on a rotatable shaft 63, forming part of adrive mechanism 64,

tion output of motor 55 in the form of rotation of shaft 63. In atypical case, driving mechanism 64 will include a train of reductiongears or equivalent for converting the many revolutions of a typicalservomotor to approximately one revolution of shaft 63, and therefore ofcam 62, over the entire range of core movement.

A lever 66, having one end pivoted at 67 for deflection of its other endin the plane of rotation of cam 62, has a spherical or cylindricalfollower 68, pivoted for rotation on a pin 69 fixed to the said otherend of lever 66, said pin oriented so that follower 68 rotates about anaxis parallel to the axis of rota-tion of cam 62. The cam and levers arearranged so that the follower 68 rests on the periphery of cam 62.Taking a vertical line through the center of rotation of cam 62, thepivot 67 is so located that the line or point of contact between cam 62and follower 68 is offset (as indicated at O in FIGURE 1) slightly fromsaid vertical line, the offset being to that side of the vertical linesuch that the tangent to the surface of the cam at the contact betweenit and follower 68 is more nearly parallel to the lever arm of the leverthan it would be if the offset were zero or on the other side of saidvertical line. The offset allows the deflection of points on lever 66 tobe treated as vertical displacements with less error than otherwise,whereas the more nearly horizontal the said tangent, the more nearly thesaid vertical displacement remains fixed in the face of thermalexpansion of the structural elements involved.

Suitable support means (not shown) are provided for rotatably supportingthe shaft 63 and pivot 67 in positions that are fixed in space relativeto each other.

Cam 62 is a simple linear rise cam, i.e., if cam 62 is rotatedcounterclockwise from the position shown, the radius of the peripheralpoint of cam 62 contacted by follower 68 decreases in direct linearproportion to the angle of rotation of the cam for most of a revolutionthereof.

At some intermediate point of lever 66, a pivot 70 is provided forpivoted connection of said lever to a slug or core assembly, to bedescribed later, the axis of pivoting being parallel to the pivot axisat pivot 67. Hence, as cam 62 is rotated, the pivot 70 is displaced in aslightly arcuate path that may be considered straight and verticalwithin the limits defined by the total rise of cam 62.

A pair of LVDT supports 71 and 81 are provided for supporting LVDTs 31and 41 with their coil or winding assemblies coaxially arranged oneither side of the lever. Since supports 71 and 81 are identical exceptthat one is inverted with respect to the other, a description of support71 will suffice for both.

Support 71 comprises a fixed bracket composed of plates 72 and 73,secured at their ends at right angles to each other, and fixed in spacerelative to the cam shaft 63 and pivot 67 by support means (not shown).A third plate 74 has one end thereof pivoted at 75 to the upper end ofplate 73, the axis of pivoting being oriented so that plate 74 can bedeflected in the plane of deflection of lever 66.

A screw '76 cooperates with tapped holes in plates 72 and 74 to fix theangular position of plate 74 while permitting adjustment of its angularposition, play between said plates being taken up by one or more springs79 compressed between plates 72 and 74. Screw 76 includes a threadedportion 78, tapped into plate 72, and a threaded portion 77, tapped intoplate 74, the pitch of the latter threaded portion being coarser thanthat of the former in order that as the screw is turned, the length ofthreaded portion 79 passing through plate 74 will be greater than thatpassing through plate 72. One (or both) of the holes tapped in plates'72 and 74 for screw 76 is made a slightly loose tit for the screwportion threaded therein, in order to allow for the tilting of the screwaxis as screw 76 is turned.

a The free end of plate 74 terminates in an apertured portion 74A, inwhich the cylindrical winding assembly meral 86. Device 86, which willbe described later, is

connected to pivot 70, and at either end to spacers 8'3 and 84. a

Each of the said spacers are generally cylindrical with threaded pinelements, such as shown in broken line at 88, tapped into core 44, therealso being provided flats such as shown at 89 on those parts of spacersadjacent core ends to reduce eddy currents in the spacers. Each spacerelement may be alike in respect of the said pins and flats.

At its upper end spacer 82 is terminated by a reduceddiameter, verticalguide element 92 passing through a hole 91 in fixed plate 90. Betweenthe plate 90 and a washer 93 on guide element 9 2, a spring 94 isarranged to urge the spacer 82 toward lever 66 and device 86; device 86having a threaded pin 87, tapped into spacer 83.

The remainder of the core assembly, namely spacers 84 and 85, and core44 are supported by device 86. However, an adjustable stop screw 97,arranged to thread up and down, through a fixed plate 96, limits thedownward travel of core 44, device 86 being provided with.

overthrow or escapement means that all-ow lever 66 to continue to letcore 34 and its spacers down, even though the lower end of spacer 85 isin contact with the other end of stop screw 97.

FIGURE 2 illustrates connecting and escapement device 86 in detail,wherein the body of the device is shown to be a generally cylindricalbody 100, having threaded pin 87 at its upper end for connection tospacer 83, and an axial bore 101 in the lower end thereof. Spacer 84 isprovided with a vertical extension 102 loosely received in bore 101.

A pair of vertically extending slots "103 are provided opposite eachother in the bored part of body 100, and extension 102 of spacer 84 hasafiixed thereto a cross pin 104, the ends of which pass through slots103. Body 100 also has a cross pin 105 which is affixed to the body atany convenient point past the upper extremity of extension 102. a Crosspin 104 is urged against the lower endsvof slots 103 by means of aspring 106 compressed between a pair of washers 108 and 107 between andabutting the respective pins 104 and 105. Spring 106 is chosen to beweaker than spring 94 (\FIGURE 1).

Assuming that in the configuration of parts shown in FIGURE 1, therealso obtains the configuration of parts shown in FIGURE 2,counterclockwise movement of cam 62 obviously cannot cause lever 66 tolet down core 44, since stop screw 97 will not permit. However, as cam62 rotates, spring 94, which is stronger than spring 106, forcesfollower 68 to remain in contact with the cam because the force ofspring 94 causes body 100 to move down and, via pin 105 and washer 107,to compress spring 106, slots 103 permitting such motion.

For the purposes t illustration, take the position of cam 62 shown inFIGURE 1 to be that corresponding to the maximum value of square root,and take the arrangement to be such that the secondary voltages of theLVDTs are equal and have the same phase. Since, it is desired, as cam 62begins to move counterclockwise, that both said voltages will decreasein linear proportion to'the cam angle until some convenient point suchas that where the cores 34 and 44 have moved downward through, say, 90%of their possible range of movement, stop screw 97 is far enoughdownward from the position shown in FIGURE 1 that the lower end ofspacer does not strike the upper end of the stop screw until the cammoves counterclockwise for of one full turn thereof. During thismovement, spring 106 will hold pin 104 against the lower ends of slots103, whereby cores 34 and 44 will move as one and cause both of LVDTs3'1 and 41 to cooperate to produce a voltage that represents the squareof the core movement. Upon further downward motion, however, stop screw97 prevents further downward movement of core 44, whereas core 34continues downward alone. Therefore, the voltage output change of thetransformer assembly is now proportional to the first power of theposition change of core 34 causing saidvoltage output change.

A further guide bore 91 may be provided in plate 90 to receive the guideelement of a third LVDT (not shown), the core assembly of which would beconnected to a member 98 pivoted at 99 on lever 66, for the purpose oftransmitting a square root signal to some remote apparatus such as acontroller, indicator or the like. Obviously, any or several of a numberof types of transmitting devices, which specifically diifer from LVDTsmay be actuated by the position output ot lever 66 or by the angularposition output of shaft 63, for the purpose of converting said positionoutput or said angular position to various types of signals representingcore position.

FIGURE 3 is an end view (from the left as seen in FIGURE 1) of support71 (and of support 81, inverted). The aperture in plate portion 74A isshown in broken line and denoted by the reference numeral 7413. Plate 73is seen to have upstanding ears 73A through which pivot pin 75 passes topivotally support the right extremity (as seen in FIGURE 1) of plate 74,and there is seen to be two springs 79 loading the plate assembly.

The set screw 80 is used to roughly position the cylindrical body of theLVDT 31 (not shown in FIGURE 3) in aperture 74B, and likewise in thecase of support 81 and LVDT 41. Initially, with stop screw 97backed-cit, the zero flow radius of cam 62 in contact with follower 68,LVDTs are adjusted roughly as aforesaid to vertical positions wheretheir secondary voltages are close to null. The screw 76 of support 71(and its counterpart in support 81) are then used as fine adjustments toget an exact null. Supposing the LVDTs to be linear, their secondaryvoltages will remain in a constant ratio to one another (1:1, if theLVDTs are identical) as the cam 62 is rotated to bring increasing riseto follower 68. This state of adjustment having been reached, stop screwmay be turned up until it just contacts the bottom of spacer 85 at thedesired point, as more particularly explained hereinbe-fore.

The height of adjustment of stop screw 97 depends on the particular useof the transformer assembly. The example herein is for the flowmeasuring system disclosed in my aforesaid patent and is merelyillustrative.

It will be noted that adjusting the mechanism involves establishing azero point for cam 62 at LVDT null. If cam 62 were a non-linear cam,say, with a rise proportional to the square of the cam angle, relatingcam zero and LV'DT null would be quite difiicult. That is, while intheory a square function cam and one balancing LVDT could be used toextract square root, one point on the cam would have to be exactlylocated in terms of LVDT output. Any error in locating that point wouldbe a progressively varying error due to the nature of the nonlinear riseof the cam, and this error would be in addition to those involved inprofiling the cam in manufacture.

With the linear cam 62, however, there is no zero error due to the factthat the rate of rise of the cam is constant.

The only consideration in choosing a cam zero would be to orient it sothat enough cam travel is left to cause the LVDT cores to move fullrange, in direct proportion to cam angle.

A little reflection will show that any conceivable nonlinear linka'geposes a problem in zeroing it. In the particular case of a non-linearcam, it would also be diflicult to switch over from square root to firstpower operation as simply and accurately as this is done in the systemof FIGURE 1.

The foregoing description will enable those skilled in the art topractice my invention in the best form known to me thus far. It will beevident to those skilled in the art that various modifications of theinvention may be made without departing from the scope and spirit of theinvention and its objects as these appear herein. I therefore desirethat the claims appended hereto be construed accordingly, at least tothe extent permitted by the limitations directly expressed therein.

'1 claim:

1. A core assembly for a variable transformer arrangement including apair of transformers, each having a movable core and a plurality ofwindings inductively coupled together to a degree depending on theposition of said core relative thereto, said core assembly comprising apair of cores coupled together for simultaneous movement of both inconsequence of motion applied to either core, and escapement meansmechanically coupling said cores, said escapement means including aresilient memher and a pair of elements, one on each core, saidresilient member being supported between said elements and so arrangedas to oppose movement of one of said elements toward the other of saidelements, whereby motion of one of said elements is transmitted via saidresilient member to the other of said cores.

2. The invention of claim 1, wherein said elements are looselyinterlocked together so as to permit limited movement of said elementstoward and away from each other, and said resilient means is arranged soas to force said elements away from each other to the extent of saidlimited movement.

3. The invention of claim 1, wherein one of said elements has anelongated slot, and the other of said elements has a pin projecting intosaid slot, said resilient means being arranged to force said pin againstone extremity of said slot, said slot extending along the direction ofcore movement.

4. The invention of claim 1, in combination with circuit meansinterconnecting said windings such that if one of said windings of onesaid transformer has a voltage applied thereto, one of said windings ofthe other said transformer will produce a voltage representative of theproduct of said core positions.

5. The invention of claim 4, wherein said elements are looselyinterlocked together so as to permit limited movement of said elementstoward and away from each other, and said resilient means is arranged soas to force said elements away from each other to the extent of saidlimited movement.

6. The invention of claim 4, wherein one of said elements has anelongated slot, and the other of said elements has a pin projecting intosaid slot, said resilient means being arranged to force said pin againstone extremity of said slot, said slot extending along the direction ofcore movement.

7. In a combination, wherein there are provided a first transformer anda second transformer, each said transformer having a first winding, asecond winding, and a core, said core being positionable such as tovariably couple said windings together; wherein there is providedcircuitry coupling the voltage of a said first winding of one saidtransformer across a said first winding of the other said transformer,whereby A.C. voltage across one said second winding will cause an AC.voltage to appear across the other said second winding representative ofthe product of the positions of said cores; and wherein there isprovided means movable through a range of positions, said means beingconnected to said cores for positioning each said core simultaneouslythrough a range of positions;

the improvement in said combination,

wherein said means includes escapement means, said escapement meansbeing constructed and arranged to effectively disconnect the first saidmeans from but one said core when said first said means is in a givenportion of its said range of positions;

wherein there is stop means arranged to stop motion of the other of saidcores when the said first said means moves into said given portion ofits said range of positions; and

wherein said escapement means is constructed and arranged to effectivelydisconnect said other of said cores from said first said means inresponse to stopping of motion of said other of said cores.

References Cited by the Examiner FOREIGN PATENTS 449,324 6/1948 Canada.

LEWIS H. MYERS, Primary Examiner.

JOHN F. BURNS, ROBERT K. SCHAEFER,

LARAMIE E. ASKIN, Examiners.

C. TORRES, Assistant Examiner.

1. A CORE ASSEMBLY FOR A VARIABLE TRANSFORMER ARRANGEMENT INCLUDING APAIR OF TRANSFORMERS, EACH HAVING A MOVABLE CORE AND A PLURALITY OFWINDINGS INDUCTIVELY COUPLED TOGETHER TO A DEGREE DEPENDING ON THEPOSITION OF SAID CORE RELATIVE THERETO, SAID CORE ASSEMBLY COMPRISING APAIR OF CORES COUPLED TOGETHER FOR SIMULTANEOUS MOVEMENT OF BOTH INCONSEQUENCE OF MOTION APPLIED TO EITHER CORE, AND ESCAPEMENT MEANSMECHANICALLY COUPLING SAID CORES, AND ESCAPEMENT MEANS INCLUDING ARESILIENT MEMBER AND A PAIR OF ELEMENTS, ONE ON EACH CORE, SAIDRESILIENT MEMBER BEING SUPPORTED BETWEEN SAID ELEMENTS AND SO ARRANGEDAS TO OPPOSE MOVEMENT OF ONE OF SAID ELEMENTS TOWARD THE OTHER OF SAIDELEMENT, WHEREBY MOTION OF ONE OF SAID ELEMENT IS TRANSMITTED VIA SAIDRESILIENT MEMBER TO THE OTHER OF SAID CORES.